const s1 = Symbol('张三')
const s2 = Symbol('张三')
console.log(s1 === s2)
const secretKey = Symbol('secret')

// 多人协作中 Why Symbol?
// 动态 不太安全？
// key string 类型 | Symbol 类型
const a = '123'
const user ={
    [secretKey]:'123456',
    name:'张三',
    email:'123@qq.com',
    age:18,
    [a]:'男'
}
console.log(user[a])
user.email = '456@qq.com'
console.log(user)